Attachment for a lift truck



March 3, 1959 A. w. THRESHER ETAL 2,375,912

' ATTACHMENT FOR A LIFT TRUCK Filed Jan. 23, 1956 2 Sheets-Sheet 1 INVENTORS ALBERT W THRESHER HOWARD W THRESHER A TTOP/VEYS March 3, 1959 A. w. THRESHER ETAL 5 9 ATTACHMENT FOR A LIFT TR CK Filed Jan. 23, 1956 Y 2 Sheets-Sheet 2 I IINVENTORS ALBERT W THRESHER HOWARD W THRESHER A 7' TORNEVS 2,875,912 7 ATTACHMENT FOR A LIFT TRUCK Albert W. Thresher and Howard W. Thresher,

Gridley, Calif.

Application January 23, 1956, Serial No. 560,726

1 Claim. (Cl. 214-654) The invention relates to mechanism attachable to a lift truck for clamping, lifting and rotating containers and, more particularly, to mechanism for lifting, transferring and dumping boxes of the kind utilized in connection with the bulk handling of agricultural commodities such as walnuts, almonds, prunes, rice, grains, seeds, beans, etc.

Industrial lift trucks have long been used to lift and transport objects; and a number of them have been providedwith attachments capable of grabbing the sides of the objects and inverting the objects in order to effect dumping of the contents. The difficulty with side-grabbing jaws, however, is that the interposed object, for example, a box, cannot be stacked by side clamping jaws in close juxtaposition to adjacent boxes on each side. Furthermore, if boxes are stacked in close lateral juxtaposition, the side acting grab jaws cannot be inserted in the tight space on each side of the box to be moved so as to effect withdrawal of the box from the stack.

It is therefore an object of the invention to provide an attachment for -a lift truck which clamps an interposed object, such as a box, in a vertical'direction.

It is another object of the invention to provide an attachment which may be installed on substantially any type of industrial lift truck.

Itis still another object of the invention to provide a bulk box dumping attachment which is relatively inexpensive to manufacture and install.

It is yet another object of the invention to provide an attachment for lifting and rotating boxes containing agricultural or other commodities with a high degree of accuracy and control.

It is a" further object of the invention to provide an attachment for clamping boxes securely even though there may exist some inaccuracy in box construction, or misalignmentin the box configuration due, for example, to sagging of the box as the commodity inside the box shifts during box rotation or other handling.

It is ajstill further object of the invention to provide an attachment for dumping boxes which. uses hydraulic actuating mechanism toreifect its purposes, and which supplies hydraulic fluid force through a simple yet highly effective fluid distributor which minimizes the possibility of hose entanglement. g

It is a yet further object of the invention to provide a box handling attachment which effects a positive kind of clamping unobtainable where flexible wire cables are utilized to transmit clamping force.

It is a further object of the invention to provide a generally improved attachment for an industrial lift truck.

Other objects, together with the foregoing, are attained in the embodiment described below and illustrated in the accompanying drawings, in which Figure l is a front perspective of our attachment installed on a typical lift truck.

Figure 3 is a median section of the hydraulic fluid distributor and attendant structure including the frame pivot mechanism.

Figure 4 is a front elevation of the device showing a box in elevated and rotated, or dumping, attitude.

Figure 5 is a top rear perspective of the box clamping mechanism.

Figure 6 is a diagrammatic showing of the hydraulic system, and illustrating how the devices hydraulic components are integrated into the existing system of a typical lift truck.

While the box handling attachment of our invention is susceptible of numerous physical embodiments depending on the environment and uses to be encountered, a considerable number of the-herein shown and described devices have been made and used and have performed in an eminently satisfactory fashion.

The attachment, generally designated 12, is mounted on a conventional industrial self-powered lift truck 13 having the usual body framework 14 mounted on ground.

engaging wheels 16. Mounted adjacent the front end of the customary truck is a vertically disposed mast 17, or standard, having mounted thereon, for vertical translation, a carriage 18 whose position is governed by a hydraulic plunger and cylinder mechanism 19 regulated by appropriate control levers 21 readily accessible to the operators hands.

Although the carriage 18 is translatable in a vertical direction it possesses no freedom of motion in rotation such as is required for inversion or tipping of the boxes handled by the device. Consequently, we have provided, forward of the carriage 18, a frame 26 rotatably mounted on a pivot mechanism 27, secured to the carriage 18,.

aperture 32 in a vertical plate 33 forming a part of the. carriage 18. Serving to support the central portion of the stationary shaft 31 is an axle 34 abutting againstan annur.

lar shoulder 36 on the shaft to prevent translation of the shaft in'a right-hand direction. The axle 34 is supported by a web 37 secured by fastenings 38 to carriage bracing members 39. Journaled for rotation on the machined peripheral surface 41 of the axle 34 is a bearing 42 confined against endwise motion by the web- 37 on one side and on the other-side by a flange 43 secured by fastenings 44- to the axle 34.

Mounted on the rotatable bearing 42 is a plate 51 forming the main body member of the rotating frame 26. A gear 52 having on its periphery a plurality of sprocket teeth 53 is likewise mounted on the bearing 42 and is the: operative mechanism for effecting rotation of the bearing 42 and frame 26 about the horizontal axis 28.

As appearsmost clearly in Figures 1, 2 and 4, the gear 52 is rotated by a chain 56 reeved about the gear teeth 53 and driven by a drive gear 57 rotatably mounted on the carriage 18. The drive gear 57 is itself rotated, through appropriate speed reducing mechanism 58, by a hydraulic motor 59 served by the customary pair of fluid lines 60 and governed by the conventional valves and hand levers, such devices being standard in the art and therefore requiring no further explanation. The fluid lines 60 are made long enough and are supported in such a fashion,.as appears most clearly in Figure 2, to serve the hydraulic motor 59- from lowermost to uppermost location of the carriage 18.

Serving to underlie the box 61 to be handled and to support thebox in upright attitude is a fork 62 comprisfrom the bottom of a pair of upright members 64 conveniently pivoted on a pair of pins 66 each supported between a vertical bracing member 67 and the adjacent vertical rail 68 stififening the vertical side of the frame platefsl. Conveniently the lower surface 71 of each tine is tapered, while the upper surface 72 is planar to form a close fit with the bottom panel 73 of the box.

Boxes of the kind exemplified herein are beginning to be used ever more widely in connection with the barvesting, hauling and general handling of orchard crops such as prunes, walnuts and almonds, and even some types of row crops. Where, for example, walnuts in times past have been placed in relatively small field boxes picked up from time to time, the present labor saving trend is to spot large sturdy boxes of the kind here illustrated at strategic locations in the orchard, or, where mechanized nut harvesters are used, at a marshalling area where a number of such boxes are filled as the mechanical harvesters discharge their loads. The full boxes are ordinarily then transported by truck to a central receiving station where the nuts may be dehydrated and perhaps hulled. While the box handling attachment of our invention could be used at any of the foregoing stations, it finds especial utility at the central receiving station, where, to cite an example, it is used to unload from the trucks the full boxes weighing several hundred pounds, and carrying the boxes either to a hopper for dumping or to a storage area for stacking until the contents can be handled by the dehydrator or huller.

The boxes 61 are each conveniently cubical in shape and in addition to the usual interior bracing members (not shown) is provided on its bottom with a plurality of longitudinal stringers 76 and transverse cleats 77 to form a pallet structure 78 with a pair of longitudinal openings 79 through which project the lifting prongs of the fork.

While the fork adequately supports the box in vertical translation, perhaps the most useful attribute of the device is its ability to clamp the box to the fork to permit inversion of the box and so dump its contents.

In order to effect clamping we have provided a clamping mechanism, generally designated 81, comprising a pair of slides 82 vertically translatable in a pair of guide sleeves 83 mounted on the side rails 68 of the frame 26. The upper ends of the slides 82 are connected by a cross member 84 and projecting forwardly from the pair of slides is a pair of clamping brackets 86. Clamping engagement with the top edges of the box is provided by a pair of horizontal clamping arms 87 mounted on the forward ends of the brackets. arily, the arms 87 are fixed in parallel relation with the upper surface 72 of the fork and where the box is not distorted in shape will adequately effect clamping; Where, however, the box is damaged, weakened or otherwise distorted it has been found that correction for misalignmerit can usually be made by pivoting the arms 87 on a pair of pins 88 at the ends of the brackets and providing suitable stops (not shown) limiting the extent of rotation. A pair of cross braces 89 extending between the front and rear ends of the arms causes the arms to tilt in unison although if the braces are made of small stock some relative twisting can take place to permit secure clamping by both arms even though irregularities such as non-parallelism of the boxs top edges might exist.

While quick dumping of a box can be effected merely by'inverting it, it has been found that dumping of all the contents at about the same instant is undesirable. Preferably, the contents, such as n'uts, dried fruits, etc. are poured out in a stream from the lower side of the box, and as appears most clearly in Figure 4. In order to elfect an even stream of materials it has been found that the use of a plate 91 extending between the clamping arms 87 is highly useful. In the form of plate shown herein the plate 91 is made narrower in width Custom- 4 than the distance between the arms so as to leave a predetermined opening 92 through which the material can pour as the box is rotated in the direction indicated by the arrow 93 in Figure 4. Conveniently, the plate 91 can be moutned in a track and provided with suitable latching mechanism (not shown) to permit. the opening 92 to be formed adjacent whichever arm will be the lower one as rotation of the box takes place. A simpler construction effecting a somewhat comparable result is that involving moving the arms closer together than the width of the box but covering the entire distance between the arms with plate; in this event, the fork is slid under the box elf-center so that as clamping is efiected a space or opening exists between one or the other of the arms and the adjacent box top edge, the opening serving as a channel to permit passage of the material in a measured stream. The operator places the box in off-center position and then rotates the box so that the opening or channel is on the lower side.

Vertical movement of the clamping unit, designated 96, and shown most clearly in Figures 1 and 5, is'elfected by a plunger 101 terminating at its upper end in a bifurcated bracket 102 pivotally mounted on the cross member 84 to rotate within limits about a fore and aft pin 103. Despite the slides 82 and the guide sleeves 83, some rocking of the clamping unit takes place to conform to box configurations and the pivot connection just described gives the desired freedom of motion.

Upwardly or downwardly acting force is transmitted to the plunger 101 by a hydraulic cylinder 106 which itself is mounted at its lower end on structure giving freedom of motion about at least two axes. The lower end of the cylinder terminates in a plate 107 pivotally mounted on a fore and aft pin 108 extending between a bifurcated bracket 109 which in turn is mountedon a sleeve 111 encompassing a transverse horizontal pin 112 extending between a piar of vertical bracing stiles 113. The hydraulic cylinder, in other words, has some latirude to tilt to compensate for misalignment and the clamping unit on the upper end of the plunger is also free, within limits, to accommodate imperfections in box configuration, a highly important feature since boxes are, more often than not, irregular in outline. The stresses on the mechanism and box are thereby eliminated.

Hydraulic force is transmitted to the appropriate side of the plunger head by an upper line 116 and a lower line 117, each leading from the opposite side of a hydraulic distributor 118 fabricated and integrated with the pivot mechanism 27.

Formed interiorly in the stationary shaft 31 is a longitudinal passageway 121 connected by a short transverse channel 122 to an annular chamber 123 in communication with a port 124 threaded for engagement with a nipple 126 mounted on the end of the line 116 leading to the top side of the clamping cylinder. In comparable fashion, the line 117 is fed by fluid leading through a longitudinal passageway 131, channel 132, annular chamber 133, port 134 and nipple 136. The passageways 121 and 131 are furnished fluid through a line 137 and 138, respectively, the lines 137 and 138 being led over a suitable grooved sheave 141 adjacent the top of the mast, to minimize hose entanglement, and thence'lead to the customary control and actuating mechanism.

The annular chambers 123 and 133 are formed in a hollow cylindrical block 151, or cap, mounted with a ground fit on the shaft 31 and the block rotates in unison with the frame. A plurality of O-rings 152 in annular grooves 153 straddling the annular chambers prevent seep or loss of fluid and an end plate 154 covers the forward end of the distributor, the end plate being stationary and mounted on the end of the fixed shaft 31 by suitable fastenings 156. Owing to the provision of the annular chambers, fluid pressure in the lines 116 and 117 leading to the clamping cylinder is at all times in correspondence with the pressure in the feed lines 137 and 138 despite the angularity of the frame 26. Consequently, the clamping force on the box can be regulated to a high degree of precision even though the box is turned through 360 of arc in either direction of rotation. Hose entanglement, furthermore, is thereby completely eliminated.

It can therefore be seen that we have provided a box handling attachment for an industrial lift truck which is not only highly flexible and eflicient in operation but which also gives to the proprietor of an agricultural commodity or other type of bulk handling station an eminently useful and wholly satisfactory piece of equipment.

What is claimed is:

An attachment for an industrial lift truck having a vertically movable carriage and a source of hydraulic pressure fluid, said attachment comprising a frame, means for mounting said frame on said carriage for rotation about a fore and aft axis, a first box supporting member rigidly mounted on one side of said frame, a pair of clamping brackets extending parallel to and over said first box supporting member, means for mounting said clamping brackets to slide on said frame toward and away from said first box supporting member, a second box supporting member substantially overlying and being substantially coextensive with said first box supporting member, said second box supporting member extending in a forward direction in an amount sufiicient to span both transverse margins of an open box interposed between said first and said second box supporting members, means for pivotally connecting said second box supporting member substantially on a transverse axis centrally of said second box supporting member to the extremities of said clamping brackets, a hydraulic cylinder mounted at one end on said frame and at the other end connected to move said clamping brackets simultaneously, a hydraulic distributor disposed on said fore and aft axis, means for connecting said distributor to said source of hydraulic pressure fluid, and means for connecting said distributor to said cylinder.

References Cited in the file of this patent UNITED STATES PATENTS 1,878,994 Abbe Sept. 27, 1932 2,335,572 Schroeder Nov. 30, 1943 2,468,326 Gleason Apr. 26, 1949 2,589,342 Christensen Mar. 18, 1952 2,604,220 Frischmann July 22, 1952 2,609,114 Backofen et al. Sept. 2, 1952 2,684,165 Hill July 20, 1954 2,724,520 Overbeck Nov. 22, 1955 2,753,065 Brady July 3, 1956 2,807,382 Schenkelberger Sept. '24, 1957 FOREIGN PATENTS 714,482 Great Britain Sept. 1, 1954 

